The following anal cancer prevention information is provided to help you understand the risk factors and learn about the preventative measures you can undertake to reduce your chances of getting anal cancer.
RISK FACTORS
HPV
Anal cancer is predominantly caused by human papillomavirus (HPV). In fact, it is estimated that over 93% of anal cancer cases are caused by HPV. HPV is the most common sexually transmitted infection. Nearly all adults will have HPV at some point in their lifetime. In the US, 79 million people, or 1 in 4 Americans, are currently living with HPV. In the UK, HPV is present in 1 in 3 people and 90% of individuals will come into contact with some form of the virus in their lifetimes.
There are over 100 strains of the HPV virus. For the majority of the population, the immune system will rid the body of the virus and HPV will not progress to cancer. For other individuals, HPV can lie dormant in their bodies and resurface as an HPV-related cancer decades later. HPV strains, and the infections they cause, can be classified as either low risk or high risk. Low-risk strains of HPV may manifest as genital warts. High-risk strains may turn into cancer.
HIV
It is more likely that a person with an immunocompromised system, such as people with human immunodeficiency virus (HIV) will develop anal cancer. A strong immune system is important to fight off opportunistic infections such as HPV.
Other Cancers
Certain studies indicate that the risk of anal cancer is higher for women who have had cervical, vaginal or vulval cancer. This is most likely due to the risk factor shared by all these cancers; HPV infection.
Age / Gender
The majority of people diagnosed with anal cancer are over the age of 50.
Incidence rates of anal cancer are higher in women than men.
Smoking
Smoking increases your chances of developing anal cancer, as carcinogens (cancer-causing chemicals) in tobacco can affect the entire body. There is evidence that smoking may decrease the immune system’s ability to fight HPV infection. Studies have also shown that current smokers are at higher risk of developing anal cancer than former smokers and those who have never smoked at all.
PREVENTION
HPV VACCINATION
Vaccines exist to protect individuals from the most cancer-causing strains of the virus. HPV is the cause of anal cancer 93% of the time. It also causes at least five other cancers, including cervical cancer. Since it is likely most people will have at least one intimate partner during their lifetime, HPV vaccination, screening and practising safe sex are important steps that will help reduce the chance of getting HPV and anal cancer.
The HPV vaccine is available in both the US and the UK and indeed in many countries round the world. The HPV vaccines are recommended at an early age to protect against human papillomavirus because:
- Early vaccination offers the fullest protection before children are exposed to the virus. HPV is transmitted through intimate skin-to-skin contact. Data suggest that there is minimal exposure to HPV at 11 and 12 years old as few are sexually active.
- Younger people have a better immune response to the vaccine.
Please see our section on Vaccination and Understanding the HPV Vaccine for more information.
PRACTISING SAFE SEX
To decrease the risk of transmitting HPV it is important to practise safe sex and use a condom. To be most effective, condoms should be used properly during every sex act, every time. However, because HPV is transmitted through skin-to-skin contact, areas left exposed while wearing a condom during sexual activity are still vulnerable to HPV transmission.
MAINTAIN HIV TREATMENT
For individuals with HIV, maintaining antiretroviral therapy will help keep the immune system strong.
US - For more information on HIV treatment options, speak to your medical provider or visit AIDS.gov.
UK - For more information on HIV treatment options, speak to your medical provider or visit the NHS.
SMOKING CESSATION
Stopping smoking reduces your risk of developing many cancers, including anal cancer.
US - For help quitting visit the CDC website on smoking cessation.
UK - For help quitting visit the NHS website on smoking cessation.
SCREENING FOR ANAL CANCER AND PRECANCER
Screening is important for people who are past the recommended age range for the vaccine. Even with vaccination, it is important to continue regular screening. This is because you may have been exposed to a strain of the virus not covered by the vaccine, or you may have been exposed before being vaccinated.
Anal cancer can be detected and monitored in its precancerous stages. Anal precancer is called AIN or Anal Intraepithelial Neoplasia. Please see our section on Anal Precancer for more information.
Scientists are still studying which populations to screen on a routine basis, how often to screen and what types of treatment are most effective. However, if you notice bleeding or discharge from the anus, anal itching, abnormal bowel habits including constipation, a lump near your anus, or anal pressure or pain, or any other sensation that has you concerned, see your doctor immediately and ask to be examined.
How do I get screened?
If you think you may have AIN or are at risk, it is suggested that you have a clinician screen you.
Screening may involve:
- Visual inspection. However, appropriate and accurate screening may also include additional methods, as a visual check alone can fail to diagnose AIN inside the anal canal and changes that are subtle.
- Digital ano-rectal exams or 'DARE': a doctor places his or her fingers inside the anal canal to feel for abnormalities. The purpose of this test is to look for abnormal masses or growths. This exam will only find tissue that is already cancerous.
- An anal pap test: similar to a routine cervical pap test and involves sampling cells inside the anus to detect changes and abnormalities.
- Anoscopy: a tube called an anoscope is placed inside the anus and a strong light illuminates the tissue.
- High-resolution anoscopy or HRA: a more advanced anoscope with a high-resolution magnifying glass is used to examine and evaluate the tissue in the anus. This is the most precise examination for anal cancer and precancer.
Screening Guidelines
Routine screening guidelines for anal cancer or precancer have yet to be universally adopted because there have not yet been enough studies for the government and medical communities to recommend routine screening. The predominant guidelines tend to focus only on HIV-positive individuals. New York State, for example, recommends annual anal pap smears for HIV-positive men and women.
There is increasing evidence to support screening for precancers. The US National Institutes of Health (NIH) is currently funding what is known as the ANCHOR study, which will be the first randomized control trial for anal precancer screening efficacy and treatment. This is the first study that the NIH has ever supported on anal precancer screening. It is hoped that standards of care will be developed from this study and embraced by the government and medical community. Read our letters to the National Cancer Institute in support of this study from 2011 and from 2012.
Where Can I Get Screened?
Please see our Medical Resources page to find a clinician providing screening services in your area.
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